1. Field of the Invention
The present invention relates to an organic electro-luminescent display (“OELD”), and more particularly, to an OELD using two panels.
2. Description of the Related Art
Organic electro-luminescent displays (“OELDs”) are self-luminescent displays which use an organic compound as a luminescent material. OELDs are simpler, less expensive to fabricate, have lower power consumption, smaller thickness, and higher response speed than non-luminescent thin film transistor (“TFT”) liquid crystal displays (“LCDs”).
Active matrix OELDs include a plurality of organic light emitting diodes (“OLEDs”) arranged in an X-Y matrix configuration and a semiconductor circuit driving the OLEDs. The OELDs are generally classified into top emission type OELDs and bottom emission type OELDs according to the direction of light emission. Top emission type displays emit light more or less directly to an outside and bottom emission type displays emit light through a bottom substrate before reaching the outside.
Top emission type OELDs include a plurality of pixels, wherein each pixel includes a plurality of pixel circuits including a plurality of transistors and an OLED is disposed on each pixel circuit, such that the OLED overlaps the corresponding pixel circuit. On the other hand, in bottom emission type OELDs, which also include a plurality of pixels, a pixel circuit and a corresponding OLED are disposed such that they do not completely overlap each other.
In top emission type OELDs, a pixel circuit of each pixel is formed in part of the pixel. A passivation layer (or a planarization layer) is formed on the entire pixel including the pixel circuit using an insulating material. An OLED occupying a large portion of the pixel is formed on the passivation layer.
In bottom emission type OELDs, since light emitted from an OLED must penetrate a substrate, the OLED is formed such that it does not overlap an opaque pixel circuit region incapable of transmitting light.
In the fabrication of the OELD, a plasma surface treatment is performed on an anode formed of a transparent material such as indium tin oxide (“ITO”). This plasma surface treatment may damage a transistor of the pixel circuit which is covered by a passivation layer but is not covered by the anode. Although the pixel circuit is covered with the passivation layer, it may be damaged by high-energy plasma penetrating the passivation layer. Moreover, the transistor of the pixel circuit may be damaged by an organic liquid material used to form the OLED.